1. Field of the Invention
This invention relates to air conditioning units and, more particularly, to a means for providing variable proportions of fresh, i.e. outside ambient, and recirculated, i.e. inside space, air between entirely fresh air and entirely recirculated air to a space to be conditioned.
2. Background Art
The provision of outside air to a space to be conditioned through an air conditioning unit is commonly effected when the outdoor temperature and humidity conditions are such that these conditions within the space can be improved. The outside air may be provided selectively with or without refrigeration by the air conditioning unit.
One problem with conventional air conditioning units is that they typically are capable of introducing only a relatively small proportion of outside air to the amount of recirculated inside air. One such conventional unit is shown in U.S. Pat. No. 2,971,351, to Webster.
In Webster, an air conditioner is disclosed having a dual inlet blower section. An adjustable damper disk is provided at the outside air inlet and has ports selectively registrable with ports in a bulkhead to control the effective area of the inlet. No structure is provided for proportioning the amount of recirculated air delivered to the blower relative to the outside air. With this construction, the state of the outside air might dictate high volumetric delivery. However, flow of the recirculated air to the blower limits the flow of outside air thereto so that a mixture of no more than a 50% outside air mixture can be obtained.
An improvement over the Webster structure is disclosed in U.S. Pat. No. 3,440,946, to Morrison wherein an apparatus is provided with a dual inlet blower. In Morrison, spaced damper plates are associated with each of the inlets. The plates are interconnected so that reciprocable shifting of the damper control moves one plate over one inlet to adjustably restrict the same, while the other plate moves equally away from the other inlet to increase air flow.
The size and complexity of the Morrison structure are serious deficiencies with respect to modern window air conditioners. For example, the damper plates obstruct axial flow of air towards either inlet. As a result, to freely pass air through either inlet, the plate associated therewith must be moved a substantial distance away from the inlet opening. Thus, a blower of substantial length must be provided to accommodate sufficient axial shifting to provide the desired flow volume parameters. The need for increasing the blower dimensions, compromises the desirable compactness of the unit.
Further, it is believed that the volume of air flowing through the inlet does not vary gradually and consistently as the disk moves from its fully blocking positions. Rather, at some stage an abrupt change in the air flow occurs. This makes mixing unpredictable and precludes precise selection of inside and outdoor air proportions.